The cornea is a principal refractive element in the eye; corneal transparency and corneal shape determine its optical qualities. Corneal epithelial edema, stromal edema and corneal shape anomalies can independently or collectively degrade visual acuity. The focus of this application is on the metabolic features of the corneal epithelium as they relate to the maintenance of corneal hydration; the refinement and application of a mathematical model that integrates the thermodynamic description of corneal epithelial, stromal and endothelial transport properties into a model of corneal hydration control; and, finally, the development of methods to assess the optical quality of the corneal surface through the analysis of corneal topography. The following specific aims are proposed: 1) Expand understanding of corneal epithelial transport processes through continued in vitro chemical, pharmacological, and neural manipulation of rabbit tissue. 2) Adapt a mathematical model for corneal hydration dynamics to test specific corneal responses to clinical or pathological situations and incorporate a method to deal with structural modifications as they relate to corneal shape. 3) Extend the analysis of corneal topography from surface reconstructions and color coded map clinical presentations to numerical constructs that can be used for the evaluation of corneal surface optical quality as it relates to visual acuity in corneal surgery patients. It is a long term goal of this project to consider the above three specific aims within the same framework. This will allow the development of consistent formalism with which to understand the physiology of the cornea as it relates to Us optical characteristics. The rationale for the construction of a comprehensive model for corneal optics is that such a synthesis of separate knowledge derived from several experimental approaches should lead to an improved fundamental understanding of how the cornea participates in human visual performance.